https://www.sciencedaily.com/releases/2019/12/191203143311.htm

When a researcher "thinks outside the box" -- literally

Imagine having to push a wire as thin as a human hair deeper and deeper inside a very long, very narrow tube full of twists and turns. The wire's lack of rigidity, along with the friction forces exerted on the walls of the tube, will eventually render the manoeuvre impossible, with the wire ending up folded on itself and stuck in a turn of the tube. This is exactly the challenge facing surgeons who seek to perform minimally invasive procedures in ever-deeper parts of the human body by steering a guidewire or other instrumentation (such as a catheter) through narrow, tortuous networks of blood vessels.